Li Haifeng, Liang Wanqi, Yin Changsong, Zhu Lu, Zhang Dabing
School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
Plant Physiol. 2011 May;156(1):263-74. doi: 10.1104/pp.111.172080. Epub 2011 Mar 28.
Grass plants develop unique floral patterns that determine grain production. However, the molecular mechanism underlying the specification of floral organ identities and meristem determinacy, including the interaction among floral homeotic genes, remains largely unknown in grasses. Here, we report the interactions of rice (Oryza sativa) floral homeotic genes, OsMADS3 (a C-class gene), OsMADS13 (a D-class gene), and DROOPING LEAF (DL), in specifying floral organ identities and floral meristem determinacy. The interaction among these genes was revealed through the analysis of double mutants. osmads13-3 osmads3-4 displayed a loss of floral meristem determinacy and generated abundant carpelloid structures containing severe defective ovules in the flower center, which were not detectable in the single mutant. In addition, in situ hybridization and yeast two-hybrid analyses revealed that OsMADS13 and OsMADS3 did not regulate each other's transcription or interact at the protein level. This indicates that OsMADS3 plays a synergistic role with OsMADS13 in both ovule development and floral meristem termination. Strikingly, osmads3-4 dl-sup6 displayed a severe loss of floral meristem determinacy and produced supernumerary whorls of lodicule-like organs at the forth whorl, suggesting that OsMADS3 and DL synergistically terminate the floral meristem. Furthermore, the defects of osmads13-3 dl-sup6 flowers appeared identical to those of dl-sup6, and the OsMADS13 expression was undetectable in dl-sup6 flowers. These observations suggest that DL and OsMADS13 may function in the same pathway specifying the identity of carpel/ovule and floral meristem. Collectively, we propose a model to illustrate the role of OsMADS3, DL, and OsMADS13 in the specification of flower organ identity and meristem determinacy in rice.
禾本科植物会形成独特的花模式，这种模式决定着谷物产量。然而，在禾本科植物中，花器官特征决定和分生组织确定性的分子机制，包括花同源异型基因之间的相互作用，在很大程度上仍不清楚。在此，我们报道了水稻（Oryza sativa）花同源异型基因OsMADS3（一个C类基因）、OsMADS13（一个D类基因）和下垂叶（DL）在决定花器官特征和花分生组织确定性方面的相互作用。通过对双突变体的分析揭示了这些基因之间的相互作用。osmads13 - 3 osmads3 - 4表现出花分生组织确定性的丧失，并在花中心产生了大量包含严重缺陷胚珠的类心皮结构，而在单突变体中未检测到这种情况。此外，原位杂交和酵母双杂交分析表明，OsMADS13和OsMADS3既不调节彼此的转录，也不在蛋白质水平上相互作用。这表明OsMADS3在胚珠发育和花分生组织终止方面与OsMADS13发挥协同作用。引人注目的是，osmads3 - 4 dl - sup6表现出花分生组织确定性的严重丧失，并在第四轮产生了额外的一轮类似浆片的器官，这表明OsMADS3和DL协同终止花分生组织。此外，osmads13 - 3 dl - sup6花的缺陷与dl - sup6的缺陷相似，并且在dl - sup6花中未检测到OsMADS13的表达。这些观察结果表明，DL和OsMADS13可能在决定心皮/胚珠特征和花分生组织的同一途径中发挥作用。我们共同提出了一个模型来说明OsMADS3、DL和OsMADS13在水稻花器官特征决定和分生组织确定性方面的作用。
